Use of Brewers Dried Grains as an Unconventional Feed Ingredient in the Diets of Broiler Chickens : A Review

| Dried Brewers grains (DBG), a brewery by-product that, may offer a suitable cheap replacer for traditional feedstuffs (e.g., corn and soybean meal). A variety of essential nutrients are present in BDG which are required in feed formulation for poultry. It is composed of around 20% crude proteins, 6% ether extract, 15% crude fiber and 4% ash. Besides, it is fairly rich in essential amino acids; 0.9% lysine, 0.4% methionine, 0.4% tryptophan, 1.2% phenylalanine, 1.1% threonine as well as 1.6% valine. As a result, the concentrations of protein and amino acids are greater in BDG than in maize. However, the use of BDG in poultry feeds has some constraints such as high moisture and fiber contents. The high moisture content of wet brewers’ grains (about 80%) increases its bulkiness. So, efficient sun-drying is recommended to avoid nutrient losses of the by-product. Due to presence of high fiber content in BDG, it is mainly used as a cattle feed. But, there are also many studies, which explored the use of BDG in poultry diets. The present review article highlights the nutritional value of BDG as an untraditional feedstuff in broiler diets and its impacts on

wet or after drying (Peña and Posadas, 2016).Because the wet grains deteriorate easily, the product is usually dried to obtain the BDG.Spent grain or BDG contains 93% dry matter (DM), 22.4% CP, 19.1% CF, 4% ash, 48.6% nitrogen free extract (NFE), 2360 kcal/kg of metabolizable energy (ME), and 6.2% EE (Longe and Adetolla, 1983).Therefore, DBG (up to 5%) can be incorporated into the rations of quail layers by partial replacement of soybean meal, maize and de-oiled rice bran to improve egg production, productivity and higher profit margin (Swain et al., 2013).On the same context, several studies indicated that total cost of production and feed cost per Kg decreased with increasing BDG levels (Adama et al., 2007;Fasuyi et al., 2018).
BDG is high in CP and ME and consequently could be used to reduce the quantity of maize grain and soybean meal used in broiler chicken diets.However, BDG or brewery waste dryer use is limited in poultry diets because of its high fiber content.Some studies showed that BDG can be used for poultry feeds to some extent (Parson et al., 1983;Noll et al., 2001;Odunukan et al., 2016).The present review article aimed to provide a spotlight on the nutritional value of BDG as an unconventional feedstuff in broiler diets and its impacts on growth performance, carcass characteristics, nutrient digestibility, blood constituents and economics.

Agro-industriAl by-Products in Poultry nutrition
In the field of poultry industry, it is important to find alternative inexpensive feedstuffs to the commonly used ingredients in poultry diets.Many of these by-products have some constraints for their use in the ration such as: low energy, low availability of amino acids and high fiber content and high bulker presence of anti-nutritive factors (Ishibashi and Ohta, 2000).However, these limitations may be overcome by chemical, physical and biological treatments of the feeds, using an optimum proportion in diets or supplementing with the limiting amino acids; methionine and lysine.The use of industrial by-products internationally has continued to be of interest to feed manufacturers and nutritionists, and many of them are generally used as feed ingredients.The most prominent by-products of plant origins come mainly from oil seed mills and brewing industries (Adama et al., 2007;Fasuyi et al., 2018).

iMPActs of bdg on broilErs
Body weight and body weight gain: Effect of DBG levels on the growth of broiler chicks has received much attention by several research workers.Lopez and Carmona (1981) prepared basal diets containing 0, 10, 20, 30 and 40% DBG replacing wheat and soybean meal for broiler chickens.Three separate periods (0-4, 4-8 and 8-12 weeks of age) were considered.Body weight gain decreased during periods 0-4 and 4-8, when using over 20% DBG, and period 8-12, when using over 30%, but final body weight was decreased only in period 4-8.Onifade and Babatunde (1998) used three different levels (10, 20 and 30%) of BDG in broiler chicken diets and found that growth rate was similar up to 20% of BDG in diets.Kokol et al. (2012) evaluated the effect of DBG at the levels of 0, 15, 30, 45 and 60% as corn replacer on the growth performance of Anak 2000 of broiler of4 weeks of age.They found that there was no significant effect among treatment groups for live weight.Also, Ironkwe and Bamgbose ( 2011 Brewers Dried Grains (Santos et al., 2003;Mussatto et al., 2006;Swain et al., 2012).(2011) evaluated the effect of BDG at level of 0%, 25%, 50%, 75% and 100%respectively on growth performance of broiler chickens.They found that the daily feed intake decreased in response to high level of BDG, with the highest intake in 100% maize and the least value in 100% BDG.

Main analysis unit
Friesen et al. (1992) reported that the FCR was increased due to the use of BDG in poultry diets Aghabeigi et al. ( 2013) evaluated the impact of gradual replacement of soybean meal with 0, 5, 10, 15, 20 and 25% BDG on performance in broiler chickens.Feed intake value in 0 and 5% BDG groups was increased compared to other groups, but feed conversion ratio was not affected by BDG inclusion at the finisher phase (24 to 42 d).FCR of chicks fed the diet incorporated with 10% BDG was similar to those fed the basal diet, but FCR of birds fed 20% BDG increased significantly (Swain et al., 2012).Similarly feeding of 5% or 30% BDG did not affect the FCR of broilers at finisher stage (Esonu et al. 1999).In the study of Lopez and Carmona (1981), basal diets containing 0, 10, 20, 30 and 40% BDG replacing wheat and soymeal meal for broiler chickens decreased in feed efficiency during periods 0-4 and 4-8, when using 20% or more BDG, and period 8-12, when using 30% or more.Neither food intake nor dressing percentage was affected.Lower feed intake by birds at high concentrations of BDG might result from high amount of fiber present in BDG.
DBG contains high concentration of non-starch polysaccharides and some tannins which interfere with the feed utilization inhibit the absorption of essential nutrients and digestive enzymes in-vitro and in-vivo, decreasing the efficiency of feed utilization Lacassagne et al. (1998).BDG contains high concentrations of fiber.Thus, adding of enzymes could improve the utilization of BDG.In this regard, Alabi et al. ( 2014) studied the effect of (0 or 25%) BDG supplemented with four levels of different exogenous enzyme on performance, nutrient absorption and gut health of Arbor acres broilers.They found that feeding of BDG supplemented with commercial enzymes improves all parameters compared to those without commercial enzyme.
carcass traits: Lopez and Carmona (1981) used BDG at levels of 0, 10, 20, 30 and 40% in broiler chicken diets and found that insignificant differences in average dressing percentage with up to 20% inclusion level.They observed that when 20% inclusion level or more BDG was used, there were significantly reduced abdominal fat pad and meat tissue with no effect on bone tissue.Also, Chumpawade et al. (2008) showed that the use of BDG in broiler diets did not affect the carcass cuts.

EconoMics
Adama et al. (2007) analyzed feed cost in the diets incorporated with four levels of sorghum BDG up to 40% replacing maize and groundnut cake, which was certainly lower for the BDG diet, and cost per unit of body weight gain was lower all BDG gain with lowest cost for the 40% BDG diet.Ironkwe and Bamgbose (2011) replaced maize with BDG at 0%, 25%, 50%, 75% and 100% in the diets of 28 d old broilers chicks and reported that the highest intake was noted for birds fed 100% maize and the least value of intake and cost from birds fed 100% BDG., it decreased as the BDG increased in the diet.Cost per kg weight gain also showed a similar trend, and the most favorable feed cost per kg weight gain was obtained for birds on diets containing 50, 75 and 100% BDG.Overall, though BDG decrease feed efficiency and weight gain above 10 to 20% level, it is apparent that inclusion of BDG in diets would decrease feed cost per unit of body weight gain and profits for the producers.On the other hand, no significant differences were observed in broiler chickens fed diet supplemented with BDG when the rearing cost and selling price as well as the cost of feed per kg of diet were investigated (Adeniji et al., 2015).

concluSIonS
The use of BDG is a good source for protein and amino acids than corn.However, it is difficult to compare research findings regarding the use of BDG in poultry diets because of the different sources and types of the grains used during brewing process.For broiler chickens, inclusion rates of 5 to 10% of the diets.The major limitation to the use of this byproduct in poultry rations is its high fiber content.The high fiber content resulted in lower digestibility of the rations containing high amounts of BDG.A few researchers have indicated that enzyme supplementation can improve the nutritive value of BDG in poultry diets, particularly broiler starter diets.

AcKnowlEdgEMEntS
Authors extend thanks to their respected institutes and universities.

table 1 :
Chemical composition and nutritive value of

Advances in Animal and Veterinary Sciences March 2019 | Volume 7 | Issue 3 | Page 222 due
to inclusion of BDG in the diets, which are attributed to the complexation between fibrous structures of the BDG and minerals(Denstadli et al., 2010).